1. Technical Field
This invention relates to techniques for understanding vibrational information that will assist in the design, building and installation of dynamic manufacturing machinery and foundations supporting such machinery, and, more particularly, to characterization of vibration transmissivity at various machine element joints and foundation interfaces.
2. Discussion of the Prior Art
With ever increasing demand for higher product quality and machine productivity, particularly in high-volume production environments, analysis of vibrational influences has become more important. However the extent of prior art investigations of vibrational influences has been limited to attempts to understand vibrational signatures of dynamic machining and attempts to quantify low frequency vibrations in soil underlying machine foundations.
In U.S. Pat. No. 5,663,894, vibrational signatures of machines have been characterized by discriminating vibrational activity at various positions on such machines, both with and without machining loads; the vibration signature analysis included both time and frequency domain analysis which was stored in a database for future comparison and tracking. Such disclosure does not deal with vibrations that are derived from the environment and transmitted to the machine, nor does it deal with the quality of transmissivity of vibrations at various sites along the vibration transmission path.
U.S. Pat. No. 5,646,350 discloses a method to detect latent or incipient failure conditions of machinery (such as divots or flat spots on bearings) by isolating the low speed frequency vibrations from high frequency vibrations which tend to drown out the lower frequencies; acceleration units for the sensed vibrations are converted to velocity units and an estimate is made of the most probable noise floor which is then subtracted from the signal data. Again, no attempt is made to characterize the vibration transmissivity along various sites of the vibrational path and no attempt is made to investigate the influence of environmental vibrations.
In the U.S. Pat. No. 5,610,336 a method of designing foundations for machinery is disclosed, consisting of predicting the natural frequency of a proposed machine foundation through measurement of the natural frequency of the soil base (non-linear system) beneath the proposed foundation. Again no attempt is made to investigate transmissivity of vibrations from such soil base to machine elements supported by the foundation.
It is an object of this invention to provide a method of characterizing environmental and machinery vibrations by a transmissivity discriminator so that design of the machine foundation and machine structural elements can be more effectively made, based on quantitative information concerning the influence of such environmental and machine induced vibrations.
The inventive method herein that meets the above object, comprises the steps of simultaneously monitoring and capturing vibration acceleration signals at locations comprising a source site, which can be ground soil or a foundation through which environmental vibrations pass, and a target site, which can be a planned machinery foundation site or one or more sites containing interfacing joints between elements of the machinery to be placed on such foundation; extracting amplitude and frequency data from the frequency representations of the domains of such signals; quantifying displacement excitations from such data at such locations; providing transmissivity ratios along the vibration path, between the source site and target site, by summing the displacement excitations at different frequencies at each of the locations and then ratioing the sums at either the planned machinery foundation site or at a selected joint site with the sum at the environmental excitation source site, thereby indicating the relative vibration stiffness between such ratioed sites. Such transmissivity ratios can then be used to modify the design of the proposed foundation, and/or the design of interfacing machine elements.